1. Field of the Invention
The present invention relates to an external light-shielding layer, a filter for a display device including the external light-shielding layer, and a display device including the filter. More particularly, the present invention relates to a filter for a display device including an external light-shielding layer which can enhance contrast ratio in a bright room and a Moire phenomenon, and a display device including the display filter.
2. Description of the Related Art
As modern society becomes more information oriented, the technology of image display devices and apparatuses is advancing, and these devices are becoming widespread. In particular, image display devices are in widespread use in devices such as TV screens and PC monitors. Thinly built wide screens have become mainstream display devices.
In particular, a plasma display panel (PDP) is gaining popularity as a next-generation display device to replace a cathode ray tube (CRT) because it is thin, has a large screen, and can be readily fabricated. A PDP device displays images based on a gas discharge phenomenon, and exhibits superior display characteristics, e.g., a high display capacity, high luminance and contrast, free from afterimage, and a wide viewing angle.
In a PDP device, when a direct current (DC) or alternating current (AC) voltage is applied to electrodes, a gas plasma discharge occurs that produces ultraviolet (UV) light. The UV emission excites adjacent phosphors to emit visible light.
Despite the above advantages, PDPs have several challenges associated with driving characteristics, including an increase in electromagnetic (EM) radiation, near-infrared (NIR) emission, phosphor surface reflection, and an obscured color purity due to orange light emitted from neon (Ne), helium (He) or xenon (Xe) that is used as a sealing gas.
The electromagnetic (EM) radiation generated by PDPs may adversely affect humans and cause electronic devices such as wireless telephones or remote controls to malfunction. Thus, to use such PDPs, there is a need to reduce the EM radiation emitted from the PDPs to a predetermined level or less, e.g., by shielding. Various PDP filters have been used for such shielding, and to reduce unwanted reflections and enhance color purity. For example, various PDP filters having an EM shielding function and a NIR wave shielding function can be used with PDPs.
Conventional PDP filters cannot, however, prevent external light from entering a panel assembly in a bright room condition. External light that enters the panel assembly may undergo interference with light emitted from a discharge cell in the panel assembly, thereby lowering a bright room contrast, ultimately degrading the image display quality of PDPs.
Additionally, in conventional PDP filters, a Moire phenomenon is generated due to interference fringes created when two or more periodic patterns are formed between pixels and PDP filters, which may degrade image display quality of PDPs.